Various chemical and biological agents are currently being used on commercially grown fruit to control the timing of fruit ripening. Such agents can be used for a variety of purposes. One purpose is to synchronize the ripening of fruit to assist in efficient harvesting of fruit from the field. Another purpose is to prevent drop off of fruit so that fruit remain on the plant until the appropriate ripening time period. Another purpose of fruit ripening agents is to enhance color development in the fruit so the fruit has a better and more uniform color as expected by retail consumers of the fruit. In the United States, it is current practice for many types of fruit to be treated with one or more such agents during the cultivation processes.
Some agents previously used for control of fruit ripening are purely synthetic agents found to have desired effects on the fruit in question. Unfortunately, due to issues of both potential toxicity and oncogenicity, several such synthetic chemical fruit ripening agents have either been banned or had their use sharply curtailed due to commercial or consumer resistance to the products. The most popular agent currently being used to enhance fruit ripening is ethephon, a synthetic compound, which is sold under the name of Ethrel, a trademark of Rhone-Poulenc Ag. Co. (Research Triangle Park, N.C.). Although this agent stimulates ripening, it also causes the fruit to soften. Thus, fruit treated with ethephon has a very poor shelf life. There is a critical need for a ripening agent which is environmentally safe and which does not cause fruits to soften. In addition, consumers are willing to pay a premium price for vine ripened fruits. However, vine ripened fruits cannot be transported long distances because these fruits soften and have poor shelf life. Therefore, it would be beneficial to improve the shelf life of vine ripened fruits.
There is also a tremendous interest in the plant industry (especially in the fresh vegetables and cut flower industries) to find an environmentally safe product to retard senescence and promote shelf or vase life. Presently, environmentally toxic compounds such as silver thiosulfate are being used to increase the vase life of cut flowers. However, the use of silver thiosulfate is being curtailed because of environmental concerns. Therefore, it is desired to develop alternatives to silver thiosulfate, which are much more likely to be readily accepted by commercial interests and consuming public.
Lysophosphatidylethanolamines (hereinafter referred to as xe2x80x9cLPExe2x80x9d) comprise a group of compounds that have shown promise in controlling fruit ripening, enhancing fruit stability during storage, and increasing the shelf life of stored fruit. Methods for using LPE purified from egg (hereinafter referred to as xe2x80x9cLPEeggxe2x80x9d) to enhance fruit ripening and stability are disclosed in U.S. Pat. Nos. 5,126,155 and 5,100,341, which are incorporated by reference herein. LPE is derived from phosphatidylethanolamine, a lipid normally found in cell membranes. Phosphatidylethanolamine is a phospholipid with two fatty acid moieties which is abundant in egg yolk. The removal of one fatty acid from phosphatidylethanolamine by phospholipase A2 yields LPE.
LPE is also naturally present in plant and animal tissue, especially rich in egg yolk and brain tissue. It is available commercially from Avanti Polar Lipids, Inc. (Alabaster, Ala.). There are numerous different fatty acids that can be found in LPE purified from natural sources. The fatty acids can vary in the length of a chain as well as the degree of unsaturation. However, the relative efficacy of various species of LPE and also of different kinds of lysophospholipids other than LPE in the control of fruit ripening and enhancing fruit stability has not been examined.
The present invention relates to a method of delaying senescence in fruit or plant tissues. The method involves applying to the fruit and other plant tissues, either prior to or after harvest, a composition containing a lysophospholipid and an activating agent. The composition contains an amount of a lysophospholipid that is effective in delaying senescence in fruit and other plant tissues. The preferred lysophospholipid contained in the composition is lysophosphatidylinositol and/or lysophosphatidylethanolamine (18:1). In addition to containing the lysophospholipid, the composition may also contain an activating agent, such as ethanol, tergitol or sylgard 309.
Moreover, the present invention also relates to a method of enhancing the ripening and stability of fruit. The method involves applying to whole plants before harvest, a composition containing a lysophospholipid and an activating agent. The composition contains an amount of lysophospholipid that is effective in enhancing fruit ripening and stability. The preferred lysophospholipid contained in the composition is lysophosphatidylinositol and/or lysophosphatidylethanolamine (18:1). In addition to containing the lysophospholipid, the composition may also contain an activating agent, such as ethanol, tergitol or sylgard 309.